Method of dressing concrete



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COATING 0R PLASTIC. v

May 14, 1940. RlPLEY 2,200,433

IETHOD 0F DRESSING CONCRETE SURFACES Filed June 28. 1937 qL/ *0 V Oman c Maremm.

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Cancun: Sunrncz- CONCRETE Bass Canaan: Sunmc:

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NATHEN H. RlPLEY INVENTOR v "Wi /maid.

ATTORNEYS 106. COMPOSITIONS,

COATING OR PLASTIC.

Patented May 14, 1940 UNITED STATES PATENT OFFICE METHOD OF DRESSING CONCRETE UBFACES 3 Claims.

This invention relates to improved methods of treating concrete surfaces and more particularly to improved methods of re-surfwcing concrete roadways.

When concrete highways have been in use for an extended period of time, for example, about five years, the surface thereof becomes very smooth and glossy and in wet weather particularly, vehicles using the roadway show great tendency to skid. The glossy surface is produced largely by bitumen-like hydrocarbon residue found in the exhaust of most internal combustion engines and also by drippings of oil and grease from the vehicles using the roadway. In course of time these organic materials penetrate the surface of the roadway, forming an adherent bond with same, and as chemical changes including oxidation and polymerization take place a hard waterproof organic film is formed upon the road surface. In addition to the above mentioned disadvantage produced by this film of promoting skidding, the film of organic material also prevents re-surfacing of the road with inorganic materials insomuch as when fresh cement and the like is applied upon the surface it does not penetrate thru the organic layer and accordingly, very quickly chips and flakes off to the obvious detriment of the road surface.

It is the primary object of the present invention to provide a means whereby this film of organic by-products can be readily and economically removed from the road surface and a new cement surface applied which will be tenaciously and permanently bonded to the old road surface.

Other objects and advantages of the present invention will be apparent to those skilled in the art upon consideration of the following description.

The accompanying drawing diagrammatically illustrates steps in the process according to the present invention and the following description is to be read in the light of this drawing.

In accordance with the present invention, the roadway is first treated with a relatively concentrated solution of caustic alkali which serves to facilitate saponification and removal of the organic film. It is preferred to treat the road I surface with caustic for approximately six to eight hours but this period is not critical and may be varied with different concentrations of alkali and with different conditions of road surface. At the completion of the alkali treatment the alkali is removed, for example, by sweeping the road surface, and hydrochloric acid, preferably having a concentration of about five to ten per cent hydrogen chloride based upon weight, is sprayed or otherwise applied to the road surface. Altho other acids can replace hydrochloric acid, such as sulphuric or the like, hydrochloric acid is preferred. One of the purposes of the acid treatment is to facilitate the disintegration of the outer surface of concrete which contains the major part of the undesirable organic residue. It is preferred that the acid be left in contact with the road surface until the disintegration has proceeded to an extent such that a layer of approximately of an inch in thickness can be easily scraped away by a knife blade, altho this is not critical and a suitable limit of treatment will depend upon the condition of the road surface. When experiment indicates that the acid-treatment has proceeded to the desired degree a relatively thin layer of sodium orthoborate is sifted upon the road surface thereby stopping or at least diminishing the action of the acid upon the concrete and also serving to facilitate subsequent operations as will be hereinafter described.

When the road surface has been prepared by the treatment hereinbefore described, a mixture MW and r or a mixture 0 cement and wa er, or any other similar composition desired for the dressing surface is then applied. The layer of sodium orthoborate-acid mixture on the road sur ace ac a e 11 ng of the dressing layer with the concrete road surface. The reactions involved, being extremely complex, do not readily lend themselves to stoichiometric equations but it is believed by the present inventor that a possible explanation for the observed behavior of the borax in facilitating the bonding of the two cementi 1ous layers is to act as a bufiegg' gent, thereby maintaining the hydrogen ion concentration of the mixture at a relatively fixed value. It may also be that the borate portion enters into reaction with the cement to form complex boro-sg but, as hereinbefore mentioned, ese reac 1 are not readily definable with certitude.

Other materials, substantially the equivalents of those hereinbefore mentioned in connection with the preferred embodiment of the present invention will be apparent to those skilled in the art and their substitution as well as variations in the time of treatment and the like are com prehended within the spirit of the present invention.

Having thus described the present invention, what is claimed is:

1. In the process of dressing concrete surfaces having a hydrocarbon film thereon comprising substantially removing said film, the improvemen prises superficially treating said surface with powdered sodium orthoborate and the like whereby adhesion of subsequently applied cementitious material is promoted, prior to applying on said treated surface a dressing mixture including cement.

2. In the process of dressing concrete surfaces having a film of hydrocarbon residue thereon 

